Pressure regulated inflatable cuff for an endotracheal or tracheostomy tube

ABSTRACT

An elastic cuff encircles a tracheostomy or endotracheal tube near its distal end and has opposite ends fitting tightly against the tube, with the proximal end of the cuff sealed to the tube. A tubule with a distal end opening into the inside of the cuff extends therefrom outwardly along the tube and has an outer end for air under pressure for inflating the cuff. The distal end of the cuff forms a check valve stretchable radially away from the tube by excessive air pressure in the cuff if the air delivered thereto through said tubule results in a pressure drop across the valve exceeding a predetermined amount, whereupon the pressure drop will be reduced to that predetermined amount.

United States Patent 1191 Carroll 14 1 Feb. 26, 1974 1 PRESSUREREGULATED INFLATABLE CUFF FOR AN ENDOTRACHEAL OR TRACHEOSTOMY TUBE [76]Inventor: Robert G. Carroll, 240 Melwood St., Pittsburgh, Pa. 15213 [22]Filed: Aug. 2, 1972 [21] Appl. No.: 277,316

[52] U.S. Cl. 128/351 [51] Int. Cl A6lm 25/00 [58] Field of Search.128/348, 349 B, 349 BV, 351,

[56] References Cited UNITED STATES PATENTS 3,504,676 4/1970 Lomholt128/351 3,565,079 2/1971 Jackson 128/351 FOREIGN PATENTS OR APPLICATIONS1,238,411 7/197] Great Britain 128/202 Primary ExaminerCharles F.Rosenbaum Attorney, Agent, or Firm-Brown, Murray, Flick &

Peckham 5 7] ABSTRACT An elastic cuff encircles a tracheostomy orendotracheal tube near its distal end and has opposite ends fittingtightly against the tube, with the proximal end of the cuff sealed tothe tube. A tubule with a distal end opening into the inside of the cuffextends therefrom outwardly along the tube and has an outer end for airunder pressure for inflating the cuff. The distal end of the cuff formsa check valve stretchable radially away from the tube by excessive airpressure in the cuff if the air delivered thereto through said tubuleresults in a pressure drop across the valve exceeding a predeterminedamount, whereupon the pressure drop will be reduced to thatpredetermined amount.

5 Claims, 2 Drawing Figures PRESSURE REGULATED INFLATABLE CUFF FOR ANENDOTRACHEAL OR TRACI'IEOSTOMY TUBE A hospital patient requiringintermittent positive pressure ventilation may have a tube inserted inhis trachea by way of the mouth or nose or by way of a surgicallycreated opening into his trachea. The distal end of the tube isencircled by an inflatable cuff to provide a seal against the wall ofthe trachea. In making sure that such a seal is adequate, there is atendency to overinflate the cuff so that it may press too tightlyagainst the tracheal wall. Besides discomfort, this can cause seriouscomplications, such as dilation of the trachea, blockage of circulation,and necrosis of that portion of the trachea around the cuff. Variousways have been proposed to prevent overpressurizing of such cuffs, butmost of them have not been successful or have been so complicated thatthey have not been used properly.

It is an object of this invention to provide an endotracheal ortracheostomy tube with an inflatable cuff that will produce a safepressure controlled good seal against the tracheal wall that willprotect against aspiration during all phases of the ventilatory cycle.Another object is to provide such a cuff that will automatically preventoverpressurization. A further object is to provide a cuff which willautomatically cycle its internal pressure in syncronous response toairway pressure.

The preferred embodiment of the invention is illustrated in theaccompanying drawings, in which FIG. 1 is a side view of an endotrachealtube, with an overpressurized cuff shown partly in section and excessiveair escaping from it; and

FIG. 2 is an enlarged view of the cuff from the distal end of the tube.

Referring to FIG. 1 of the drawings, a flexible breathing tube 1 that isadapted to be inserted in the trachea T in a well-known manner has anouter or proximal end that is exposed for connection to breathingapparatus (not shown) by which air can be forced into the lungperiodically. The tube is encircled near its inner or distal end by anelastic cuff 2, preferably about five centimeters long and threecentimeters in diameter when inflated but unstretched and unpressurized.The opposite ends of the cuff have a much smaller diameter than the areabetween them and normally both fit tightly against the tube. The cuffcan be inflated by air forced into it by means of a syringe 3 or thelike, temporarily connected to the outer end of a very small diametertube or tubule 4 that extends along the main tube and into the inside ofthe cuff. In one make of endotracheal tube the tubule is molded into thewall of the tube and has an outlet 5 from its distal end into the cuff.After the cuff has been inflated, the syringe is removed and the outerend of the tubule is clamped or plugged to maintain the desired airpressure in the cuff.

It is a feature of this invention that the cuff cannot be overinflatedexcept momentarily. Accordingly, although the proximal end 7 of the cuffis sealed against the tube, such as by an adhesive, the major portion ofthe distal end 8 of the cuff is not attached to the tube. It need betacked to the tube at only one or two points to prevent it from slidingalong the tube. For example, a stitch or a spot of adhesive 9 may holdthe end of the cuff in place. The rest of the distal end of the cuff isfree to be stretched radially away from the tube in case the airpressure in the cuff is excessive. Consequently, the distal end of thecuff serves as a check valve. In this connection it should be noted thatit is not the air pressure alone inside the cuff that is the determiningfactor regarding opening the valve, but it is the pressure gradient ordrop across the check valve; that is, the difference in air pressurebetween the inside of the cuff and the air pressure in the trachea belowthe cuff. This pressure drop exists only during exhalation, when thepressure in the lungs drops to approximately zero. If the pressureinside the cuff at that time is greater than the cuff is designed for,the excess pressure will be relieved because it will stretch the checkvalve 8 radially away from the tube sufficiently to allow air to escapefrom the cuff until the intracuff pressure is back to a safe value.

During inflation of the lungs by the breathing apparatus, the pressuredrop across the check valve becomes zero because the air pressure in thetrachea below the cuff and the air pressure inside the cuff areequalized. In other words, as the air pressure in the trachea below thecuff starts to exceed the normal pressure within the cuff, the lower endportion of the cuff is compressed and that reduces the internal volumeof the cuff and causes the intracuff pressure to increase to balance theair pressure in the trachea. The check valve is held closed by theincreased air pressure around it. There is thus no danger of cuffdeflation when high airway pressures are necessary for patientventilation. Although at this time the pressure of the cuff against thewall of the trachea is increased, it has no more injurious effect onthat wall than the pressure of the air against it below the cuff.

It will be seen that it is absolutely necessary that it be the distal orlower end of the cuff that serves as the check valve to permit excessiveair pressure to escape from the cuff. If this valve were formed by theupper end of the cuff instead, during inflation of the lungs the airpressure in the trachea below the cuff would squeeze the air out of theupper end of the cuff and thereby deflate it.

-To control the opening of the check valve formed by the distal end ofthe cuff, it has been found best to make that end in the form of acylindrical band as shown, so that an appreciable area of the tube willbe engaged by the cuff, rather than providing merely line contactbetween them. The band may be about 5 mm long, although it may beprovided with pleats that extend from its inner edge part way out to itsfree outer edge so that the inner area of the band will expand andseparate from the tube easily as overinflation starts to occur, wherebythe threshold pressure for cuff decompression is controlled moreexactly. It also has been found best to design the cuff so that apressure drop across the check valve that does not exceed about 20 mm ofmercury during exhalation will not open the valve. If, due to too muchair being forced into the cuff through the tubule, the pressure dropbecomes greater than that, the check valve will open and permit enoughair to escape from the cuff to reduce the pressure drop to 20 mm ofmercury. Even if positive-negative pressure ventilation is used, thevalve will remain closed if the resting intracuff pressure is 15 mm ofmercury and the negative pressure during the negative phase ofventilation does not exceed 5 mm of mercury.

The cuff and tube should be made of materials that will not sticktogether where the distal end of the cuff engages the tube. If rubber isfound to present such a problem, the tube and/or cuff can be made ofsome such material as Dow Cornings Silastic.

Another important advantage of this cuff is that if the patient is notbeing ventilated effectively and if he is capable of making inspirationefforts of sufficient magnitude, he can actually suck the air out of thecuff through the check valve and thereby collapse the cuff so that hecan inhale around it.

With this cuff the intracuff pressure is independent of the skills ofthose who may inflate the cuff, because the check valve willautomatically take care of too much air pressure in the cuff.Consequently, the pressure of the cuff against the wall of the trachealikewise is controlled automatically.

According to the provisions of the patent statutes, I have explained theprinciple of my invention and have illustrated and described what I nowconsider to represent its best embodiment. However, I desire to have itunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically illustrated anddescribed.

I claim:

1. The combination with an endotracheal or tracheostomy tube havingdistal and proximal ends, of an elastic cuff encircling the tube nearits distal end and having opposite ends fitting tightly against the tubewith the proximal end of the cuff sealed to the tube,

and a tubule extending from the cuff outwardly along said tube andhaving a distal end communicating with the inside of the cuff, theproximal end of the tubule having an inlet for air under pressure forinflating the cuff, and the distal end of the cuff forming a check valvestretchable radially away from the tube by excessive air pressure in thecuff if the air delivered thereto through said tubule results in thepressure drop across said valve exceeding a predetermined amount,whereby said pressure drop will be reduced to said predetermined amount.

2. The combination recited in claim 1, including means tacking saiddistal end of the cuff to the tube to prevent it from sliding along thetube.

3. The combination recited in claim 1, in which said distal end of thecuff is in the form of a cylindrical band.

4. The combination recited in claim 1, in which said distal end of thecuff is in the form of a cylindrical band secured at at least one pointto the tube to prevent it from sliding along the tube.

5. The combination recited in claim 1, in which said distal end of thecuff is in the form of a cylindrical band provided with pleats extendingoutwardly across the band to points spaced inwardly from the outer edgeof the band.

1. The combination with an endotracheal or tracheostomy tube havingdistal and proximal ends, of an elastic cuff encircling the tube nearits distal end and having opposite ends fitting tightly against the tubewith the proximal end of the cuff sealed to the tube, and a tubuleextending from the cuff outwardly along said tube and having a distalend communicating with the inside of the cuff, the proximal end of thetubule having an inlet for air under pressure for inflating the cuff,and the distal end of the cuff forming a check valve stretchableradially away from the tube by excessive air pressure in the cuff if theair delivered thereto through said tubule results in the pressure dropacross said valve exceeding a predetermined amount, whereby saidpressure drop will be reduced to said predetermined amount.
 2. Thecombination recited in claim 1, including means tacking said distal endof the cuff to the tube to prevent it from sliding along the tube. 3.The combination recited in claim 1, in which said distal end of the cuffis in the form of a cylindrical band.
 4. The combination recited inclaim 1, in which said distal end of the cuff is in the form of acylindrical band secured at at least one point to the tube to prevent itfrom sliding along the tube.
 5. The combination recited in claim 1, inwhich said distal end of the cuff is in the form of a cylindrical bandprovided with pleats extending outwardly across the band to pointsspaced inwardly from the outer edge of the band.